Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$154.50	8.325%	$167.3621	$167.36	$167.35	$167.40
Purchase #2	$139.33	9.113%	$152.0271	$152.03	$152.05	$152.00
Purchase #3	$9.73	11.472%	$10.8462	$10.85	$10.85	$10.80
Purchase #4	$185.42	10.724%	$205.3044	$205.30	$205.30	$205.30
Purchase #5	$185.39	3.733%	$192.3106	$192.31	$192.30	$192.30
Purchase #6	$91.77	9.373%	$100.3716	$100.37	$100.35	$100.40
Purchase #7	$168.64	4.255%	$175.8156	$175.82	$175.80	$175.80
7 purchase totals =	$934.78		$1,004.0376	$1,004.04	$1,004.00	$1,004.00